# 標頭參數模型 { #header-parameter-models }

如果你有一組相關的標頭參數，可以建立一個 Pydantic 模型來宣告它們。

這能讓你在多處重複使用該模型，並一次性為所有參數宣告驗證與中繼資料。😎

/// note | 注意

自 FastAPI 版本 `0.115.0` 起支援。🤓

///

## 以 Pydantic 模型宣告標頭參數 { #header-parameters-with-a-pydantic-model }

在 Pydantic 模型中宣告你需要的標頭參數，然後將參數宣告為 `Header`：

{* ../../docs_src/header_param_models/tutorial001_an_py310.py hl[9:14,18] *}

FastAPI 會從請求的標頭為每個欄位擷取資料，並交給你已定義的 Pydantic 模型實例。

* They need to handle cleanup (e.g., DB sessions, file handles), using dependencies with `yield`
* Their logic needs input data from the request, like headers, query parameters, etc.

## Dependencies with `yield` and `scope`

When using dependencies with `yield`, they can have a `scope` that defines when the exit code is run.

        byte[] buf = new byte[length];
        Arrays.fill(buf, (byte) 0xFF);
        return buf;
    }

    @Test
    @DisplayName("constructor initialises command and parameters correctly")
    void testConstructorInitialisesFields() throws Exception {
        int level = 42;
        Trans2QueryFSInformation cmd = new Trans2QueryFSInformation(level);

/**
 * Query command implementation for handling fuzzy search queries.
 * This class converts Lucene FuzzyQuery objects into OpenSearch fuzzy query builders,
 * supporting configurable fuzzy matching parameters like edit distance and expansions.
 *
 */
public class FuzzyQueryCommand extends QueryCommand {
    private static final Logger logger = LogManager.getLogger(FuzzyQueryCommand.class);

    /**

如果您有一组相关的 **header 参数**，您可以创建一个 **Pydantic 模型**来声明它们。

这将允许您在**多个地方**能够**重用模型**，并且可以一次性声明所有参数的验证和元数据。😎

/// note | 注意

自 FastAPI 版本 `0.115.0` 起支持此功能。🤓

///

## 使用 Pydantic 模型的 Header 参数 { #header-parameters-with-a-pydantic-model }

在 **Pydantic 模型**中声明所需的 **header 参数**，然后将参数声明为 `Header` :

{* ../../docs_src/header_param_models/tutorial001_an_py310.py hl[9:14,18] *}

    }
  }

  /**
   * Asserts that the given throwable has the given class and then asserts on the message as using
   * the full set of method parameters.
   */
  private void assertFailureCause(
      Throwable throwable, Class<? extends Throwable> clazz, Object[] params) {
    assertThat(throwable).isInstanceOf(clazz);
    if (params.length == 1) {

    }
  }

  /**
   * Asserts that the given throwable has the given class and then asserts on the message as using
   * the full set of method parameters.
   */
  private void assertFailureCause(
      Throwable throwable, Class<? extends Throwable> clazz, Object[] params) {
    assertThat(throwable).isInstanceOf(clazz);
    if (params.length == 1) {

  * When annotating existing internal code, use `org.jetbrains.annotations.Contract`, e.g. `@Contract(null -> null; !null -> !null)`.
      When doing so, still annotate nullable parameters and the return type as `@Nullable`.
  * Do not use `@Contract` for public APIs.
  * For polynull public APIs, the solution has to be decided on a case-by-case basis.

     * @throws CIFSException if decompression fails
     */
    byte[] decompress(byte[] compressedData, int algorithm) throws CIFSException;

    /**
     * Decompresses data with offset and length parameters.
     *
     * @param compressedData the compressed data buffer
     * @param offset the offset in the buffer
     * @param length the length of compressed data

    // we cannot use individual @Params as some will lead to invalid combinations which do not let the benchmark terminate. JMH offers no
    // support to constrain the combinations of benchmark parameters and we do not want to rely on OptionsBuilder as each benchmark would
    // need its own main method and we cannot execute more than one class with a main method per JAR.
    @Param(
        {